Set the oven to 400°. Thinly slice as many sweet potatoes as you need. Throw them in a bowl. Drizzle olive oil on them and mix until they are coated evenly. Put the sliced potatoes on a baking sheet. Sprinkle cinnamon over the fries. Bake for about 30-45 min or until tender. A bit longer if you like them crispy. Once out of the oven, put them on a plate and sprinkle generously with brown sugar. Add a dash of salt for taste.